Plug-in circuit and cooling system thereof

ABSTRACT

The present invention relates to a plug-in circuit and a cooling system thereof. The cooling system includes the plug-in circuit, an external terminal and an alternating current (AC) compressor, wherein the plug-in circuit includes an AC to AC inverter and an inverter control circuit. The AC to AC inverter is coupled to and between the external terminal and the AC compressor for converting an external AC voltage received by the external terminal to an internal AC voltage to supply to the AC compressor. The inverter control circuit is coupled to the AC to AC inverter for outputting a control signal to the AC to AC inverter to control the frequency of the internal AC voltage according to an external parameter.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a cooling system, and moreparticularly, to a plug-in circuit and a cooling system thereof.

2. Description of the Related Art

In recent years, due to the development of technology, a cooling system,such as an air conditioner, a refrigerator, a freezer and so on, becomesan indispensable electric appliance in the present days. However, thepower consumption of the cooling system is also the largest among theelectric appliances in the present days.

FIG. 1 illustrates a circuit block diagram depicting a conventional airconditioner without inverter control. Referring to FIG. 1, the circuitis illustrated utilizing an air conditioner with splitting type as theexample. The air conditioner includes an indoor unit 11 and an outdoorunit 12, wherein the outdoor unit 12 includes an alternating current(AC) compressor 121 and a control circuit 122. The coupling relationshipof the circuit of the air conditioner is shown as FIG. 1. Thereinafter,the operational concept thereof is described. First, assume the indoortemperature is 30 degrees in Celsius, and then user uses a remotecontrol to control the indoor unit 11 to set up an indoor temperature,such as 25 degrees in Celsius. Next, the control circuit 122 starts tosupply the power voltage to the AC compressor 121, wherein the ACcompressor will be kept to operate at 100% power consumption. Ingeneral, the indoor unit 11 has a built-in temperature detector.

Assuming the indoor is lower than 25 degrees in Celsius through thecontinuous operation of the circuit, the temperature detector of theindoor unit 11 disables a start-on signal transmitted to the controlcircuit 122, and then the control circuit 122 cuts off the AC powervoltage supplied to the AC compressor 121 to disable the AC compressor121. When the indoor temperature is higher than 25 degrees in Celsius,the temperature detector of the indoor unit 11 enables the transmittedstart-on signal, and then the AC compressor 121 is operated again.

However, the cooling system without inverter control usually generatesunstable noise due to the stop-and-go AC compressor, and the indoortemperature of user's feeling varies a lot, sometimes cold, sometimeswarm. In addition, a large start-on current is so demanding when the ACcompressor is operating. Therefore, it causes extremely large powerconsumption when the AC compressor starts on and off frequently.

Due to the above-mentioned drawback, a direct current (DC) invertercontrol is provided in the prior art. Nevertheless, due to the high costof the DC inverter circuit, the price of the air conditioner withinverter control remains high. The customers of the air conditioner withDC inverter control may need 5 to 10 year to pay back their expense. Ifusers bought air conditioner with DC inverter control is unfortunatelydamaged, the customer has to pay a lot payment for repairing it. Thus, alot of people still do not want to buy the air conditioner with DCinverter control.

SUMMARY OF THE INVENTION

In view of the above-mentioned problems, the present invention isdirected to a plug-in circuit and a cooling system thereof forincreasing the efficiency of a compressor, reducing the powerconsumption of the cooling system and extending the operating life ofthe compressor.

To achieve the above-mentioned objective and others, a cooling system isprovided in the present invention. The cooling system includes a plug-incircuit, an external terminal and an AC compressor. The plug-in circuitincludes an AC to AC inverter and an inverter control circuit. The AC toAC inverter is coupled to and between the external terminal and the ACcompressor for converting an external AC voltage received by theexternal terminal to an internal AC voltage to supply to the ACcompressor. The inverter control circuit is coupled to the AC to ACcompressor for outputting a control signal to the AC to AC inverter tocontrol frequency of the internal AC voltage according to an externalparameter.

According to the plug-in circuit and the cooling system thereof in theembodiment of the present invention, the external parameter isenvironment's temperature. When the environment's temperature is higherthan the first boundary limit of temperature of a preset range, theinverter control circuit increases the frequency of the internal ACvoltage to a preset value at each preset time. When the environment'stemperature is lower than the second boundary limit of temperature of apreset range, the inverter control circuit will decrease the frequencyof the internal AC voltage to a preset value at each preset time. Inanother embodiment, the inverter control circuit is coupled to the ACcompressor and the external parameters are refrigerant pressures of theAC compressor. When the refrigerant pressure of the AC compressor islower than the first boundary pressure of a preset range, the invertercontrol circuit controls to decrease the frequency of the internal ACvoltage a preset value at each preset time. When the refrigerantpressure of the AC compressor is higher than the second boundarypressure of a preset range, the inverter control circuit controls toincrease the frequency of the internal AC voltage the preset value ateach preset time.

The essence of the present invention is to add an extra AC to ACinverter between the conventional AC compressor and the conventionalexternal terminal. Under an external environment, such as anenvironment's temperature or the refrigerant pressure of the ACcompressor, is varied, the AC driving voltage supplied into the ACcompressor is adjusted to an adapted frequency. Thus, the efficiency ofthe AC compressor is increased significantly, and the power consumptionof the cooling system is relatively reduced. In addition, the operatinglife of the AC compressor can be lasted longer since the AC compressoris not stop-and-go so frequently.

Further scope of the applicability of the present invention will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating preferred embodiments of the invention, aregiven in terms of illustration only, since various changes andmodifications within the concept and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given hereinafter and the accompanying drawingswhich are given in terms of illustration only, and thus are not limitedof the present invention, and wherein:

FIG. 1 illustrates a circuit block diagram depicting a conventional airconditioner without inverter control.

FIG. 2 illustrates a circuit block diagram depicting a cooling systemaccording to an embodiment of the present invention.

FIG. 3 illustrates a circuit block diagram depicting a cooling systemaccording to an embodiment of the present invention.

EMBODIMENT OF THE INVENTION

FIG. 2 illustrates a circuit block diagram depicting a cooling systemaccording to an embodiment of the present invention. Referring to FIG.2, the cooling system includes a plug-in circuit 20, an externalterminal 21, an AC compressor 22 and an indoor unit 23, wherein theplug-in circuit includes an AC to AC inverter 201 and an invertercontrol circuit 202. The AC to AC inverter 201 is coupled to and betweenthe external terminal 21 and the AC compressor 22. The inverter controlcircuit 202 is coupled to the AC to AC inverter 201. The AC to ACinverter 201 is used for converting an external AC voltage, such as220V, received by the external terminal 21 to an internal AC voltage IACto supply to the AC compressor 22. The inverter control circuit 202 isused for control the frequency of the internal AC voltage IAC outputtedfrom the AC to AC inverter 201. Thereinafter, an embodiment isillustrated as the example.

Assuming the cooling system is an air conditioner with splitting type,the user sets the target temperature to 25 degrees in Celsius and theindoor temperature is 27 degrees in Celsius. When the air conditionerstarts, the inverter control circuit 202 detects that the indoortemperature is 27 degrees in Celsius. Since the temperature differencebetween the indoor temperature and the target temperature is not verylarge, the compressor does not need to operate at full speed, andoperation in half speed is sufficient enough. Therefore, the invertercontrol circuit 202 outputs the control signal Cs to the AC to ACinverter 201 to set the frequency of the internal AC voltage IAC to 30Hz. When the indoor temperature increases to 28 degrees in Celsius, theinverter control circuit 202 controls the AC to AC inverter to increasethe frequency of the internal AC voltage IAC 2 Hz at every 30 seconds.When the indoor temperature reaches 24 degrees in Celsius, the invertercontrol circuit 202 controls the AC to AC inverter to decrease thefrequency of the internal AC voltage IAC at every 30 seconds.

The inverter control circuit 202 has a fuzzy control interval in theembodiment of the present invention. When the indoor temperature isbetween 24 to 26 degrees in Celsius, the inverter control circuit 202 iskept the AC to AC inverter 201 in a fixed frequency of the internal ACvoltage. And, the frequency of the internal AC voltage generally is nothigher than 60 Hz for protecting the AC compressor 22. In addition,since the embodiment is a plug-in circuit extra added to theconventional air condition without inverter control, the indoor unit 23generally has a signal line to output a start-on signal EN. In theembodiment, the signal line is coupled to the inverter control circuit202. When the indoor temperature is lower than 24 degrees in Celsius,the start-on signal is disabled, and the inverter control circuit 202controls the AC to AC inverter to stop the AC compressor.

It should be noted that although the above-mentioned embodiment is toutilize detecting the indoor temperature as the example. manufacturershave different design for the inverter control circuit 202. Therefore,the application of the present invention should not be limited to thispossible related form. In other words, it conforms to the essence of thepresent invention as long as the inverter control circuit 202 controlsthe frequency of the internal AC voltage according to the externalparameter. In order that people having ordinary skill in the art mayimplement the embodiment, another embodiment is described in thefollowing.

FIG. 3 illustrates a circuit block diagram depicting a cooling systemaccording to an embodiment of the present invention. Referring to FIG.3, the difference between the above-mentioned circuit and the circuit inFIG. 3 is the inverter control circuit 202 coupled to the AC compressor22 to detect the temperature and the refrigerant pressure of the ACcompressor 22. Generally speaking, in an open space, such as adepartment store or a supermarket, it cannot be accurate to detect theenvironment temperature. Therefore, it is able to control the frequencyof the AC voltage supplied to the AC compressor by detecting therefrigerant pressures in this embodiment.

Assuming that user sets the pressure to 60 pound per square inch (psi),the inverter control circuit 202 controls the AC to AC inverter 201 in afixed frequency of the internal AC voltage IAC, when the invertercontrol circuit 202 detects the low refrigerant pressure between 62 and68, When the inverter control circuit 202 detects that the lowerrefrigerant pressure is higher than 68 psi, the inverter control circuit202 controls the AC to AC inverter 201 to increase the frequency of theinternal AC voltage IAC a preset value, such as 2 Hz, at every 30seconds. When the low refrigerant pressure is higher than a boundaryvalue, such as 71 psi, the inverter control circuit 202 controls the ACto AC inverter 201 to increase the frequency increasing rate of thefrequency of the internal AC voltage to 1.5 times of level. When the lowrefrigerant pressure is lower than 62 psi, the inverter control circuit202 controls the AC to AC inverter 201 to decrease the frequency of theinternal AC voltage IAC the preset value, such as 2 Hz, at every 30seconds. When the low refrigerant pressure is lower than a boundaryvalue, such as 59 psi, the inverter control circuit 202 controls the ACto AC inverter 201 to increase the frequency decreasing rate of thefrequency of the internal AC voltage to 1.5 times of level.

To sum up, the essence of the present invention is to add an extra AC toAC inverter between the conventional AC compressor and the conventionalexternal terminal. Under the opening external environment outside, suchas an environment's temperature or the refrigerant pressure of the ACcompressor, is varied, the AC driving voltage supplied into the ACcompressor is adjusted to an adapted frequency. Thus, the efficiency ofthe AC compressor is increased significantly, the power consumption ofthe cooling system is relatively reduced and, the operating life of theAC compressor is extended since the AC compressor is not stop-and-go sofrequently. In addition, since the circuit in the embodiment of thepresent invention is a plug-in type which means the circuit can be addedon the previous air conditioner. Therefore, the cost of the circuit ofthe embodiment in the present invention is comparatively lower than thecost of the air conditioner with inverter control.

While certain exemplary embodiments have been described and shown in theattached drawings, it is to be understood that such embodiments aremerely illustrative of and not restrictive on the broad invention, andthat this invention should not be limited to the specific constructionand arrangement shown and described, since various other modificationsmay occur to those ordinarily skilled in the art.

1. A plug-in circuit, disposed on a cooling system, wherein the coolingsystem comprises an external terminal and an alternating current (AC)compressor, the plug-in circuit comprising: an AC to AC inverter,coupled to and between the external terminal and the AC compressor, forconverting an external AC voltage received by the external terminal toan internal AC voltage to supply the AC to the AC compressor; and aninverter control circuit, coupled to the AC to AC inverter, foroutputting a control signal to AC to AC inverter to control frequency ofthe internal AC voltage according to an external parameter.
 2. Theplug-in circuit according to claim 1, wherein the external parametercomprises environment's temperature.
 3. The plug-in circuit according toclaim 2, wherein the inverter control circuit controls the AC to ACinverter in a fixed frequency of the internal AC voltage when theenvironment's temperature varies within a preset range.
 4. The plug-incircuit according to claim 2, wherein the inverter control circuitcontrols to increase the frequency of the internal AC voltage a presetvalue at each preset time when the environment's temperature is higherthan a first boundary limit of temperature of a preset range, theinverter control circuit controls to decrease the frequency of theinternal AC voltage the preset value at each preset time when theenvironment's temperature is lower than a second boundary limit oftemperature of the preset range.
 5. The plug-in circuit according toclaim 1, wherein the inverter control circuit is coupled to the ACcompressor and the external parameter is refrigerant pressure.
 6. Theplug-in circuit according to claim 5, wherein the inverter controlcircuit controls to decrease the frequency of the internal AC voltage apreset value at each preset time when the refrigerant pressure is lowerthan a first boundary limit of pressure of a preset range, the invertercontrol circuit controls to increase the frequency of the internal ACvoltage the preset value at each preset time when the refrigerantpressure is higher than a second limit of pressure of the preset range.7. The plug-in circuit according to claim 5, wherein the invertercontrol circuit controls the AC to AC inverter in a fixed frequency ofthe internal AC voltage when the refrigerant pressure varies within apreset range.
 8. The plug-in circuit according to claim 1, wherein theAC to AC inverter sets the frequency of the internal AC voltage to apreset frequency when the frequency of the internal AC voltage is higherthan or equal to a preset frequency.
 9. The plug-in circuit according toclaim 1, wherein the cooling system further comprises a indoor unitcoupled to the inverter control circuit, wherein the indoor unit is usedfor detecting an indoor temperature to output a start-on signal to theinverter control circuit, wherein the start-on signal is disabled whenthe indoor temperature is lower than a preset value, and then the ACcompressor is disabled.
 10. The plug-in circuit according to claim 1,wherein the inverter control circuit is coupled to the AC compressor fordetecting a temperature or a refrigerant pressure of the AC compressor,when the refrigerant pressure of the AC compressor is higher than aprotected pressure, the inverter control circuit controls the AC to ACinverter to stop the AC compressor, when the temperature of the ACcompressor is higher than a protected temperature, the inverter controlcircuit controls the AC to AC inverter to stop the AC compressor.
 11. Acooling system, comprising: an external terminal, receiving an externalalternating current (AC) voltage; an AC compressor; an AC to ACinverter, coupled to and between the external terminal and the ACcompressor for converting an external AC voltage to an internal ACvoltage to supply to the AC compressor; and an inverter control circuit,coupled to the AC to AC inverter, for outputting a control signal to theAC to AC inverter to control frequency of the internal AC voltageaccording to an external parameter.
 12. The cooling system according toclaim 11, wherein the external parameter is environment's temperature.13. The cooling system according to claim 12, wherein the invertercontrol circuit controls the AC to AC inverter in a fixed frequency ofthe internal AC voltage when the environment's temperature varies withina preset range.
 14. The cooling system according to claim 12, whereinthe inverter control circuit controls to increase the frequency of theinternal AC voltage a preset value at each preset time when theenvironment's temperature is higher than the first boundary limit oftemperature of a preset range, the inverter control circuit controls todecrease the frequency of the internal AC voltage the preset value ateach preset time when the environment's temperature is lower than thesecond boundary limit of temperature of the preset range.
 15. Thecooling system according to claim 11, wherein the inverter controlcircuit is coupled to the AC compressor and the external parameter isrefrigerant pressure.
 16. The cooling system according to claim 15,wherein the inverter control circuit controls to decrease the frequencyof the internal AC voltage a preset value at each preset time when therefrigerant pressure is lower than a first boundary limit of pressure ofa preset range, the inverter control circuit controls to increase thefrequency of the internal AC voltage the preset value at each presettime when the refrigerant pressure is higher than a second boundarylimit of pressure of the preset range.
 17. The cooling system accordingto claim 15, wherein the inverter control circuit controls the AC to ACinverter in a fixed frequency of the internal AC voltage when therefrigerant pressure varies within a preset range.
 18. The coolingsystem according to claim 11, wherein the AC to AC inverter sets thefrequency of the internal AC voltage to a preset frequency when thefrequency of the internal AC voltage is higher than or equal to a presetfrequency.
 19. The cooling system according to claim 11, wherein thecooling system further comprises a indoor unit coupled to the invertercontrol circuit, wherein the indoor unit is used for detecting an indoortemperature to output a start-on signal to the inverter control circuit,wherein the start-on signal is disabled when the indoor temperature islower than a preset value, and then the AC compressor is disabled. 20.The cooling system according to claim 11, wherein the inverter controlcircuit is coupled to the AC compressor for detecting a temperature anda refrigerant pressure of the AC compressor, when the refrigerantpressure of the AC compressor is larger than a secured pressure or thetemperature of the AC compressor is larger than a secured temperature,the inverter control circuit controls the AC to AC inverter to stop theAC compressor.